This invention relates generally to digital amplifiers, and more specifically, to error correction in digital amplifiers.
Digital audio switching power amplifiers are well known and widely used. Such amplifiers receive a digital audio signal which has been pulse modulated. Most high efficiency digital audio switching power amplifiers are based on Pulse-width modulation (PWM). PWM is widely used in a variety of applications such as digital audio amplifiers and control applications including motor controllers. Many of these applications convert a sampled digital signal to a digital pulse-width modulation signal in order to obtain high efficiency and high accuracy. The PWM signal is presented to a switching amplifier that performs a level shifting function to translate the digital PWM input signal to a digital PWM signal having significantly higher voltage levels. To accomplish the power amplification, a higher voltage power supply is used in which the power supply voltage is directly used as the digital logic one value. Because power supplies have noise coupled into the voltage, the noise becomes a source of error in the switching amplifier. The digital switching amplifier has no ability to reject the power supply noise. Practical implementations of a switching amplifier generate distorted output pulse signals. These distortions result in nonlinear amplification of the modulated output signal. Therefore, most switching amplifiers have both nonlinearity and power supply noise error.